Process for separating and recovering of lead from tin or tin alloys



Patented May 30, 1933 PATENT o e v ALBERT HANAK, OF- PHILADELPHIA,PENNSYLVANIA PROCESS FOR SEP ABATING- AND RECOVER No Drawing.Application filed December 1-5, 1930,

One object of the invention is to com letely separate and recover,primarily, lea but also other metals, like zinc for instance,from tin,antimony or certain alloys of tin and u alloys of antimony. Anotherobject of the invention is to lower the lead content of said metals andalloys to any desired amount and thereby render them industrially moreuseful. A third object is to purify said metals or alloys by removingany lead and other constituents like zinc, cadmium, etc., which arepresent as chance impurities only.

' Both in-the primary or ore smelting, as. well as in the, secondarynon-ferrous smelt- 16 ing industry, there are produced certain metalsand alloys which are unsuited for" many industrial applications. Thus,if tin or antimony ores contain appreciable amounts of lead, orresidues'and byproducts 1 20 containing-chiefly tin or antimony or theiralloys, beco'meadmixed with lead-containing materials, the metals-andalloys resulting from the smelting of such material will contain leadand very often this, detracts fromtheir value and usefulness.- Uptothepresent time, no simple'and economical processwas knownto remove andrecover such lead. The methods which 'are in general use to purify tin,antimony 'and'their alloys 2 so do not remove and recover lead. Theelecgtrolytic refinin may accomplish the separation, of lead om tin orantimony but it requires agreat capital outlay to conduct it on acommercial scale and it is otherwise also 85 very costly and involved,e?ecially in case of rather fin ure inetals an alloys. When u the leadan. other -constituentS amount to 25% or even more, it becomes not onlyimractical but impossible to use the electro- 410 ytic method ofseparation. Tin and lead as well as antimony and lead"? form solidsolutions and eutectic -mixtures.- Tin; antimony and lead form, besidesolid solutions and terna eutectics, intermetallic compomids. The oreoing explains why n lead cannot be sepa' te fromitin, antimony andtheirvarious oys be physico-metallurg'ical means, such as 1i nation,fractional crfishtellizatiom-centrifug separatiom-etc.

e common methods of purification and 1 me or LEAD rnom m n on rm. Annexe4 Serial No. 502,627. Renewed ombu- 12, 1932.

7 separation b chemico-metallurgical means,

such as oxi ation, sulphurization, etc., are also of no avail becausetin and antimony are" a more reactive towards oxygen, etc., than leadis. I discovered, that vapors of anyhdrous metallic chlorides existingin their highest state of oxidation such as stannic-chloride (SnCh) orantimonic-chlo 'de (SbCl conducted through a metal li (e molten tin,antimony or their various alloys containing lead, zinc, cadmium andother constituents, will combine with said lead, zinc, etc., to formlead-chloride, zinc-chloride, etc. The anhydrous metallic chlorides inturn are either completely reduced to metal or to a lower vstate ofoxidation according to the equations.

Pb SbCls PbCl SbCl 7 I vThe reactions appear to be nonreversible at anyconcentration. 1

The anhydrous metallic chlorides such as stannic and antimonic chloridesare liquids at ordinary temperature and their bolling pointsare but alittle above the boilin point of water. They are easily obtaine fromtheir components and in their anhydrous form, they are noncorrosive uponthe ordinary materials of construction. Inview of these, the process canbe carried-out in a very simple and cheap equipment. The latter mayconsist "of an ordinary cast iron melting kettle to melt and hold themetal to be treated, said kettlebeing provided with a .tightfittingcover. Throu'h said 0 yer 1 passes one or a plurality of pipescon'nectedto a suitably heated container,',said pipes extending-into the moltenmetal. Said cover is also provided with one or a plurality of outletswhich are connectedto a suitable condensing apparatus to condense andre-' claim. any such reagent which passed through the molten metalunaltered or which formed during the process and 'volatilizesfl I at thetemperatures prevailing in said melt ing kettle. The anhydrousmetallic-chloride is-placedin the container and is heated to its boilingpoint. The.- vapors passing through the metal 'will combine with thelead 26 pounds of unaltered chloride.

or zinc, etc., if any present, such chlorides being lighter than themetal and remain on the surface of it from whence they can be removed,or they may volatilize in which case they are recovered by condensationas stated above.

As a specific example of my invention, 10,000 pounds of an alloycontaining 92% tin, 6% lead and 2% antimony and heated.

to 498C. was treated as described with the vapors of 400 ounds ofstannic chloride and obtained 9, 60 pounds ofan alloy containing 97.90%tin and 2.1% antimony, also 804'pounds of lead-chloride and recoveredanhydrous stannic It is evident from the foregoing that variousmodifications and combinations of the process are possible which comeunder the broader spirit of the invention. When a chloride is reduced toa lower form of oxidation from a higher form, nascent chlorine forms. Itis this nascent chlorine which combines with the lead or zinc or otherconstituents and the behavior of this nascent chlorine is utterlydifferent from the behavior of elemental chlorine. Elemental chlorinewill react in an alloy oftin and lead with the tin primarily, whilenascent chlorine reacts with the lead only. Stannic and antimonicchlorides are convenient sources of nascent chlorine.

What I claim is: i

1. The process of separating and-recovering lead from tin or alloys oftin consista ing in subjecting said tin or alloys of tin in the moltenstate to the action of vapors of anhydrous stannic chloride.

2. The process of purifyingimpure tin and alloys of tin consisting insubjecting said tin and alloys of tin in the molten state to the actionof vapors of anhydrous stannic chloride.

ALBERT HANAK.

